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The man page of pmset states:

pmset must be run as root in order to modify any settings.

Yet I cannot find out how to alter the CPU_Speed_Limit variable. I'm not a registered Apple developer, but I have searched some of their archives with no success.

$ pmset -g therm
Note: No thermal warning level has been recorded
Note: No performance warning level has been recorded
2020-11-24 13:10:40 +0100 CPU Power notify
    CPU_Scheduler_Limit     = 100
    CPU_Available_CPUs  = 8
    CPU_Speed_Limit     = 35

BACKGROUND: The reason I wish to know the answer to my question is because my MacBook Pro (15-inch, Early 2011) High Sierra 10.13.6 is throttling my CPU unnecessarily as it's running very cool (roughly 50˚C via smcFanControl). I am running my MBP on AC power and without a battery as I'm waiting for a replacement battery from a third-party. I'm not sure if my AC adapter is an original Apple power adapter, and I'm not sure if that is affecting the SMC. I've cleared NVRAM and done an SMC reset (without battery), but I still have the above issue. The battery I removed was an original Apple battery, albeit with a third party adapter at the time. The battery was grossly swollen to the point where the touchpad wasn't working.

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    If there is no battery connected, the MacBook throttles the performance to ensure that there are no unexpected and high power consumption peaks (e.g. when overclocking) which could lead to having insufficient AC power and therefore crashing the whole system. I had the same experience with a MacBook Air 11" also from 2011.
    – X_841
    Commented Nov 24, 2020 at 12:30
  • I can partially accept that, but my MBP was running fine until recently with the kernel security fix Apple provided for High Sierra. Might you be able to provide a link to an official source of this information?
    – bento
    Commented Nov 24, 2020 at 12:33
  • You mean it didn't limit the performance even the battery was disconnected?
    – X_841
    Commented Nov 24, 2020 at 12:35
  • The confusing thing is: $pmset -g sysload 2020-11-24 13:35:04 +0100 combined level = OK - user level = OK - battery level = OK - thermal level = OK
    – bento
    Commented Nov 24, 2020 at 12:35
  • @X_841 Yes, that's the strange thing. I also haven't entirely ruled out if the SMC isn't damaged. The battery I removed was an original Apple battery, albeit with a third party adapter at the time. The battery was grossly swollen to the point where the touchpad wasn't working.
    – bento
    Commented Nov 24, 2020 at 12:38

1 Answer 1

Reset to default
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I cannot find out how to alter the CPU_Speed_Limit variable.

You can't.

It's not a variable in the sense that modifying it will increase/decrease your performance. It's more of an indicator as to what the limit is currently; it's similar to your battery's current charge status - what it is at the time it was measured.

As correctly stated in the comments, your Mac will limit performance when the battery is missing: Broken battery - downgraded performance

Unfortunately, you'll just have to wait until the replacement battery arrives and you install it to regain full performance from your Mac.

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  • Your source information has led me through a curious route as I'm currently researching SMC keys. From an academic perspective they might be a sort of vector. At this time, your answer seems sufficient, but I'll need through the upcoming weekend to review if an SMC key might provide an alternate possibility of altering CPU_Speed_Limit albeit via indirect means.
    – bento
    Commented Nov 25, 2020 at 14:34

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